System and method for heat treating semiconductor

ABSTRACT

A supply system in a heat-treating apparatus for a semiconductor process has a combustor ( 12 ), heating unit ( 13 ), and gas distributor ( 14 ). The combustor ( 12 ) has a combustion chamber ( 59 ) disposed outside a process chamber ( 21 ). The combustor ( 12 ) generates water vapor by reaction of hydrogen gas and oxygen gas in the combustion chamber ( 59 ), and supplies it to the process chamber ( 21 ). The heating unit ( 13 ) has a heating chamber ( 61 ) disposed outside the process chamber ( 21 ). The heating unit ( 13 ) selectively heats a gas not passing through the combustion chamber ( 59 ) to a temperature not lower than an activating temperature of the gas, and supplies it to the process chamber ( 21 ). The gas distributor ( 14 ) selectively supplies the hydrogen gas and oxygen gas to the combustion chamber ( 59 ), and selectively supplies a reactive gas and inactive gas to the heating chamber ( 61 ).

TECHNICAL FIELD

[0001] The present invention relates to a heat-treating apparatus andmethod for a semiconductor process which heat-treat a target substratesuch as a semiconductor wafer. The semiconductor process refers tovarious types of processes performed to form a semiconductor layer,insulating layer, conductive layer, and the like on a target substratesuch as a semiconductor wafer or LCD substrate with a predeterminedpattern. This aims at manufacturing a semiconductor device or astructure including an interconnection, electrode, and the like to beconnected to the semiconductor device on the target substrate.

BACKGROUND ART

[0002] In the semiconductor process, a vertical heat-treating apparatusis known as a batch type processing apparatus. The batch type processingapparatus heat-treats a large number of semiconductor wafers at once by,e.g., oxidation, diffusion, annealing, and CVD. In the verticalheat-treating apparatus, a large number of wafers are arrayed and heldat predetermined gaps in the vertical direction in a holding tool calleda wafer boat. This holding tool is loaded into a vertical processchamber. The wafers are heat-treated while being heated by a heatingmechanism disposed around the process chamber.

[0003] As a process which forms a silicon oxide film (SiO₂ film) byoxidizing a silicon wafer, a dry oxidation process and wet oxidationprocess are known. In the dry oxidation process, oxygen (O₂) gas andhydrogen chloride (HCl) gas are supplied to the process chamber. In thewet oxidation process, water vapor and oxygen gas are supplied to theprocess chamber. The dry oxidation process and wet oxidation process areselected in accordance with the target film quality.

[0004] In the dry oxidation process, a silicon wafer and layer areoxidized by the oxygen gas, while surface impurities are removed by thegettering effect of chloride. More specifically, for example, a largenumber of wafers are held like shelves by a wafer boat, and are loadedin a vertical process chamber. A processing atmosphere with apredetermined temperature is formed in the process chamber.Subsequently, oxygen gas and hydrogen chloride gas are supplied at roomtemperature into the process chamber from its ceiling, and are exhaustedfrom the lower side.

[0005] The wet oxidation process requires an external combustor outsidethe process chamber. Part of the oxygen gas and the hydrogen (H₂) gasare burned by the combustor to generate water vapor. The remainingoxygen and water vapor are supplied into the process chamber.

[0006] As another heat treatment, an oxinitriding process is known.According to the oxinitriding process, dinitrogen monoxide gas (N₂O gas)is introduced at room temperature into the process chamber. Theintroduced gas reacts with the silicon layer of the wafer to form asilicon oxide film (silicon oxinitride film) containing nitrogen.

Disclosure of Invention

[0007] It is an object of the present invention to provide aheat-treating apparatus and method for a semiconductor process, withwhich when a target substrate is to be heat-treated by an oxidationprocess or the like, the process temperature can be decreased.

[0008] According to a first aspect of the invention, there is provided aheat-treating apparatus for a semiconductor process, comprising:

[0009] a process chamber which accommodates a target substrate;

[0010] a support member which is disposed in the process chamber andsupports the target substrate;

[0011] a heater which heats the target substrate accommodated in theprocess chamber;

[0012] an exhaust system to evacuate an interior of the process chamber;and

[0013] a supply system to supply a process gas into the process chamber,

[0014] wherein the supply system comprises

[0015] a combustor which is disposed outside the process chamber and hasa combustion chamber, the combustor serving to generate water vapor byreaction of hydrogen gas and oxygen gas in the combustion chamber andsupply the water vapor to the process chamber,

[0016] a heating unit which is disposed outside the process chamber andhas a heating chamber, the heating unit serving to selectively heat agas not passing through the combustion chamber to a temperature notlower than an activating temperature of the gas and supply the gas tothe process chamber, and

[0017] a gas distributor which selectively supplies hydrogen gas andoxygen gas to the combustion chamber and selectively supplies a reactivegas and inactive gas to the heating chamber.

[0018] According to a second aspect of the invention, there is provideda heat-treating apparatus for a semiconductor process, comprising:

[0019] a process chamber which accommodates a target substrate;

[0020] a support member which is disposed in the process chamber andsupports the target substrate;

[0021] a heater which heats the target substrate accommodated in theprocess chamber;

[0022] an exhaust system to evacuate an interior of the process chamber;and

[0023] a supply system to supply a process gas into the process chamber,

[0024] wherein the supply system comprises

[0025] a combustor which is disposed outside the process chamber and hasa combustion chamber, the combustor serving to generate water vapor byreaction of hydrogen gas and oxygen gas in the combustion chamber andsupply the water vapor to the process chamber,

[0026] a heating unit which is disposed outside the process chamber andhas a heating chamber, the heating unit serving to selectively heat inthe heating chamber a gas not passing through the combustion chamber andsupply the gas to the process chamber,

[0027] a gas distributor which selectively supplies hydrogen gas andoxygen gas to the combustion chamber and selectively supplies anoxidizing gas, an oxinitriding gas, a compound gas containing hydrogenand chloride, and an inactive gas to the heating chamber, and

[0028] a controller which controls the combustor, the heating unit, andthe gas distributor so as to use the combustor and the heating unitselectively.

[0029] According to a third aspect of the invention, there is provided aheat-treating method for a semiconductor process, comprising the stepsof:

[0030] accommodating a target substrate in a process chamber;

[0031] heating the target substrate accommodated in the process chamber,

[0032] performing a wet oxidation process of oxidizing the targetsubstrate to form an oxide film by supplying water vapor to the processchamber while making hydrogen gas react with oxygen gas to generate thewater vapor by a combustor which is disposed outside the process chamberand has a combustion chamber, and

[0033] subjecting the target substrate to a first process other than awet oxidation process by supplying a reactive gas to the process chamberwhile heating the reactive gas to a temperature not less than anactivating temperature of the reactive gas by a heating unit which isdisposed outside the process chamber and has a heating chamber.

BRIEF DESCRIPTION OF DRAWINGS

[0034]FIG. 1 is a vertically sectional side view showing a verticalheat-treating apparatus according to an embodiment of the presentinvention;

[0035]FIG. 2 is an exploded perspective view showing a process unit usedin the heat-treating apparatus shown in FIG. 1;

[0036]FIG. 3 is a sectional view showing a combustor used in theheat-treating apparatus shown in FIG. 1;

[0037]FIG. 4 is a sectional view showing a heating unit used in theheat-treating apparatus shown in FIG. 1;

[0038]FIGS. 5A to 5C are diagrams showing the gas supply states of thecombustor and heating unit for different processes;

[0039]FIGS. 6A and 6B are diagrams showing the gas supply states of thecombustor and heating unit for other different processes;

[0040]FIGS. 7A and 7B are graphs respectively showing an inter-planaruniformity and planar uniformity as experimental results obtained when adry oxidation process is performed by using the heat-treating apparatusshown in FIG. 1;

[0041]FIGS. 8A and 8B are graphs showing experimental results obtainedwhen an oxinitriding process is performed by using the heat-treatingapparatus shown in FIG. 1 and by turning on/off the heating unit;

[0042]FIG. 9 is a graph showing an experimental result obtained when adiluted wet oxidation process is performed by using the heat-treatingapparatus shown in FIG. 1; and

[0043]FIGS. 10A to 10C are graphs for explaining problems of aconventional dry oxidation process.

BEST MODE FOR CARRYING OUT THE INVENTION

[0044] The present inventors studied problems of a dry oxidationprocess, wet oxidation process, oxinitriding process, and the like of avertical heat-treating apparatus in development of the presentinvention. The present inventors eventually obtained the followingfindings.

[0045] In the heat treatment of a semiconductor wafer, the higher theprocess temperature, the more likely a defect called slip tends to occurin the wafer, and the larger the thermal influence on a film on thewafer. Hence, to decrease the process temperature is currently understudy. When, however, the process temperature is decreased, the processuniformity (planar uniformity) on one target substrate (e.g., betweenthe center and periphery of the wafer) decreases. The decrease in planaruniformity becomes prominent as the diameter of the wafer increases.When the process temperature is decreased, the process uniformity(inter-planar uniformity) among a plurality of target substrates (e.g.,between upper and lower wafers in the batch process) also decreases.

[0046] It is assumed that, in the vertical heat-treating apparatus,oxygen gas and hydrogen chloride gas are supplied to the wafers on thewafer boat from the upper side of a reaction tube (process chamber),thus performing a dry oxidation process. In this case, the higher theposition of the wafer on the wafer boat, the worse the planar uniformityof the thickness of the silicon oxide film. The reason for this may beas follows.

[0047]FIGS. 10A to 10C are graphs for explaining problems of aconventional dry oxidation process. FIGS. 10A, 10B, and 10Cschematically show a gas flow on a wafer W, the temperature of the waferW, and the film thickness of the wafer W, respectively. Oxygen gas andhydrogen chloride gas flow from the periphery to the center of the waferW (see FIG. 10A), and silicon on the wafer W is oxidized by the oxygengas. As heat of the wafer W is dissipated from the periphery, the wafertemperature increases toward the center (see FIG. 10B) of the wafer. Theoxidation reaction is thus promoted more at the center of the wafer W.Hence, the silicon oxide film tends to be thicker at the center than atthe periphery (see FIG. 10C).

[0048] Hydrogen is generated by decomposition of hydrogen chloride.Oxygen reacts with this hydrogen to generate water vapor, although in asmall amount. On the upper side of the wafer boat, the gases are notsufficiently heated. As the gases are heated from the periphery towardthe center of the wafer W, the generation amount of water vaporincreases. The water vapor has an effect of growing the oxide film. Adifference in generation amount of water vapor largely influences thefilm thickness. As a result, in a wafer W on the upper side, the filmthickness is larger at the center, resulting in a so-called hill-likefilm thickness distribution (poor planar uniformity).

[0049] The process gases are heated more as they flow toward the lowerside of the reaction tube. On the lower side of the wafer boat, thewater vapor generating reaction reaches a substantial equilibrium state.More specifically, before the gases flow along the wafer W, they havealready generated water vapor almost completely. In a wafer W on thelower side, when the process gases flow from the periphery toward thecenter of the wafer W, a difference in water vapor generation amountdepending on the position of the wafer W is small. Hence, a differencein thickness caused by a difference in water vapor generation amount isalso small. Therefore, the lower the position of the wafer, the betterthe planar uniformity of the thickness of the silicon oxide film on thewafer W.

[0050] In the oxinitriding process of forming a nitrogen-containingsilicon oxide film (silicon oxinitride film) by using dinitrogenmonoxide gas, when the process temperature is decreased, the sametendency is observed. In this case, when the dinitrogen monoxide gasdecomposes, oxygen and silicon react to form a silicon oxide film.Simultaneously, the active species of nitrogen generated bydecomposition enter the silicon oxide film. Thus, the silicon oxinitridefilm grows.

[0051] In this process as well, the temperature of the wafer W is highertoward the center of the wafer W, as described above. If the processtemperature is low, the dinitrogen monoxide gas is not sufficientlydecomposed at the upper side of the wafer boat. Hence, in the wafer W onthe upper side, as the dinitrogen monoxide gas flows toward the center,its decomposition is promoted. As a result, in the wafer W on the lowerside, the film thickness is larger at the center, resulting in aso-called hill-like thickness distribution (poor planar uniformity).

[0052] The dinitrogen monoxide gas is heated more as it flows toward thelower side of the reaction tube. Hence, on the lower side of the waferboat, gas decomposition progresses sufficiently, or better, even if notsufficient, than on the upper side. Accordingly, in the wafer W on thelower side, when the dinitrogen monoxide gas flows from the peripherytoward the center of the wafer W, a difference in gas decompositiondepending on the position of the wafer W is small. Accordingly, adifference in film thickness caused by the difference in gasdecomposition is also small. Therefore, the lower the position of thewafer, the better the planar uniformity of the thickness of the siliconoxinitride film on the wafer W.

[0053] In this manner, when the process temperature is decreased, theplanar uniformity of the process for the wafer on the upper sidedegrades, and the inter-planar uniformity also degrades. Hence, theprocess temperature is currently difficult to decrease.

[0054] An embodiment of the present invention constructed on the basisof the above findings will be described with reference to theaccompanying drawing. In the following description, constituent elementshaving substantially the same functions and arrangements are denoted bythe same reference numerals, and a repetitive description will be madeonly if necessary.

[0055]FIG. 1 is a vertically sectional side view showing a verticalheat-treating apparatus according to an embodiment of the presentinvention. This heat-treating apparatus has a vertical heat-treatingunit 11, combustor 12, heating unit 13, and gas distributor 14 which arecontrolled by a main controller 57. This heat-treating apparatus canperform a wet oxidation process, dry oxidation process, and oxinitridingprocess selectively. In the wet oxidation process, hydrogen gas andoxygen gas are burned by the combustor 12 to generate water vapor. Awafer is oxidized by using the water vapor. In the dry oxidationprocess, oxygen gas (oxidizing gas) and hydrogen chloride gas (acompound gas containing hydrogen and chloride; gettering gas) are heatedby the heating unit 13. The wafer is oxidized by using these gases. Inthe oxinitriding process,.dinitrogen monoxide gas (oxinitriding gas) isheated by the heating unit 13. The wafer is oxinitrided by using thisgas.

[0056]FIG. 2 is an exploded perspective view showing the heat-treatingunit 11 used in the heat-treating apparatus shown in FIG. 1. As shown inFIGS. 1 and 2, the heat-treating unit 11 has a vertical heat-treatingfurnace 2. The heat-treating furnace 2 is connected to the gasdistributor 14 through a first gas supply pipe 41, and to an exhaustmeans 15 through an exhaust pipe 20. A wafer boat 3 as a support tool orholding tool for wafers W is detachably arranged in the heat-treatingfurnace 2. The wafer boat 3 is vertically moved by a wafer boat elevator30 disposed at the lower portion of the heat-treating furnace 2.

[0057] The vertical heat-treating furnace 2 includes a vertical reactiontube (process chamber) 21 made of, e.g., quartz, and having an openlower end. A heater 22 serving as a heating means formed of, e.g., aheating resistor, is disposed to surround the reaction tube 21. Athermally uniformizing tube 23 is disposed between the reaction tube 21and heater 22. The thermally uniformizing tube 23 is supported at itslower end by an insulator 24.

[0058] A gas diffusion plate 21 c having a large number of gas holes 21b is disposed in the reaction tube 21 slightly below an upper wall 21 a.The first gas supply pipe 41 extends through the insulator 24 from theoutside and is bent inside the insulator 24 into an L shape. The firstgas supply pipe 41 then stands vertically upright between the reactiontube 21 and thermally uniformizing tube 23. The distal end of the firstgas supply pipe 41 projects into a space between the upper wall 21 a andgas diffusion plate 21 c of the reaction tube 21.

[0059] As shown in FIG. 2, the wafer boat 3 has, e.g., a top plate 31, abottom plate 32, and a plurality of columns 33. The columns 33 connectthe top plate 31 and bottom-plate 32. A plurality of grooves are formedin the columns 33 at gaps in the vertical direction. The edges of thewafers W are inserted in these grooves, so the wafers W are heldhorizontally. The wafer boat 3 is placed on a lid 34 through, e.g., aheat insulating cylinder 35 serving as a heat insulating member. The lid34 opens/closes an opening 25 at the lower end of the reaction tube 21.The heat insulating cylinder 35 is placed on a turntable 36, and isrotated by a driving section M through a rotating shaft 37. The drivingsection M is provided to the elevator 30. The lid 34 is attached to theelevator 30. When the elevator 30 is moved vertically, the wafer boat 3is loaded in or unloaded from the heat-treating furnace 2.

[0060]FIG. 3 is a sectional view showing the combustor 12 used in theheat-treating apparatus shown in FIG. 1. As shown in FIG. 1, thecombustor 12 is connected, outside the vertical heat-treating unit 11,to the upstream side of the first gas supply pipe 41 made of, e.g.,quartz. As shown in FIG. 3, the combustor 12 has a concentricdouble-structure portion 50 formed of an inner pipe 51 a and outer pipe51 b made of, e.g., transparent quartz. An inner heating space 52A isformed inside the inner pipe 51 a. An outer heating space 52B is formedbetween the inner and outer pipes 51 a and 51 b.

[0061] The inner heating space 52A communicates with a first gas inletpipe 71 as it extends forward. The outer heating space 52B isconstricted on its upstream side, and communicates with a second gasinlet pipe 72. The second gas inlet pipe 72 extends at the right anglefrom the constricted portion. A gas flow channel extends from the firstgas inlet pipe 71 to the reaction tube 21 through the inner heatingspace 52A and first gas supply pipe 41. Another gas flow channel extendsfrom the second gas inlet pipe 72 to the reaction tube 21 through theouter heating space 52B and first gas supply pipe 41. These gas flowchannels correspond to the first gas flow channel.

[0062] For example, a helical carbon wire heater 53 is disposed on theouter surface of the outer heating space 52B, and is covered by acylindrical insulator 54. For example, the heater 53 has a string-likebody and a helical quartz pipe. The string-like body is formed byknitting together a plurality of bundles of carbon fibers containing asmall amount of metal impurities. The quartz pipe accommodates and sealsthe string-like body. The heater 53 generates heat upon reception of avoltage through a power supply line 55 connected to a power controller56. A main controller 57 for controlling this heat-treating apparatusoutputs a signal corresponding to a preset heating temperature that itdesignates. A temperature sensor 58 in the vicinity of the heater 53 andformed of, e.g., a thermocouple outputs a temperature detection signals.The power controller 56 controls a power supply amount to the heater 53on the basis of these signals.

[0063] The inner and outer heating spaces 52A and 52B communicate with adownstream combustion chamber 59. When wet oxidation is to be performedby using hydrogen gas and oxygen gas as the process gases, the hydrogengas and oxygen gas cause combustion reaction in the combustion chamber59 to generate water vapor.

[0064]FIG. 4 is a sectional view showing the heating unit 13 used in theheat-treating apparatus shown in FIG. 1. As shown in FIG. 1, the heatingunit 13 is connected to the upstream side of a second gas supply pipe 42made of, e.g., quartz. The second gas supply pipe 42 branches from thefirst gas supply pipe 41 between the vertical heat-treating unit 11 andcombustor 12. The heating unit 13 has a heating chamber 61 connected tothe second gas supply pipe 42 and made of, e.g., transparent quartz. Asshown in FIG. 4, the heating chamber 61 is formed of a cylindricalheating pipe. This heating pipe has an inner diameter larger than thatof a third gas supply pipe 73 and is elongated in the gas passingdirection. The third gas supply pipe 73 introduces the process gases. Agas flow channel extends from the third gas supply pipe 73 to thereaction tube 21 through the heating chamber 61 and second gas supplypipe 42. This gas flow channel corresponds to the second gas flowchannel.

[0065] A breathing resistance member 62 is disposed in the heatingchamber 61. When heated, the breathing resistance member 62 serves as aheating medium. The breathing resistance member 62 also applies abreathing resistance to the gasses passing through it. The breathingresistance member 62 is formed of an aggregate of a large number ofpieces made of quartz, a ceramic material, or the like. In thisembodiment, the breathing resistance member 62 is formed by fusing alarge number of quartz pieces (e.g., beads). For example, when thesecond gas supply pipe 42 has an inner diameter of 20 mm, the heatingchamber 61 has an inner diameter of, e.g., 60 mm to 80 mm and a lengthof, e.g., about 100 mm to 200 mm in the breathing direction. Each quartzbead to be filled in the heating chamber 61 has a diameter of, e.g.,about φ1 to φ10.

[0066] A carbon wire heater 63 which forms a heating means is helicallywound around the outer surface of the heating chamber 61. For example,the heater 63 has a string-like body and a helical quartz pipe. Thestring-like body is formed by knitting together a plurality of bundlesof carbon fibers containing a small amount of metal impurities. Thequartz pipe accommodates and seals the string-like body. In FIG. 4,reference numerals 64 and 65 denote a power supply unit and a terminal,respectively, to the heater 63.

[0067] The heating chamber 61 and heater 63 are covered by a cylindricalcasing 60. The casing 60 is made of, e.g., a sintered insulator ofhigh-purity silicon oxide (SiO₂). A cooling jacket 66 is formed in thecasing 60. A coolant, e.g., cooling water, flows through the coolingjacket 66 along the heater 63 (in the breathing direction). Coolingwater is supplied to the cooling jacket 66 from a cooling water supplyunit 67. A temperature detector 68, e.g., a thermocouple, is disposedbetween the cooling jacket 66 and heater 63 in the casing 60. Thetemperature detector 68 detects the temperature in the casing 60. On thebasis of this temperature, the main controller 57 outputs a controlsignal to the power supply unit 64 and cooling water supply unit 67through a supply amount controller 69. Thus, the power supply amount tothe heater 63 and the cooling water supply amount to the cooling jacket66 are controlled. That is, the heating chamber 61 is adjusted to apredetermined temperature by the mutual operation of heating by theheater 63 and cooling by the cooling jacket 66.

[0068] The heating chamber 61 of the heating unit 13 and the breathingresistance member 62 filled in it form a heat exchanger for gasespassing through them. More specifically, the process gases areintroduced through the third gas supply pipe 73 into the heating chamber61 adjusted to the predetermined temperature. The process gases and theheated breathing resistance member 62 come into contact with each other.Therefore, the process gases can be preheated to a predetermined hightemperature of 300° C. to 1,100° C., typically 800° C. to 1,000° C.

[0069] As shown in FIG. 1, the gas distributor 14 is disposed upstreamof the combustor 12 and heating unit 13. More specifically,opening/closing valves VA, VB, and VC are connected to the first,second, and third gas inlet pipes 71, 72, and 73, respectively. Thefirst gas inlet pipe 71 is connected to a hydrogen gas source 81. Avalve V1 and a mass flow controller MF1 as a flow controller areconnected midway along the first gas inlet pipe 71. The second gas inletpipe 72 is connected to an oxygen gas source 82. A valve V2 and a massflow controller MF2 as a flow controller are connected midway along thesecond gas inlet pipe 72. The third gas supply pipe 73 branches into,e.g., four pipes, so it is connected to a nitrogen gas source 83,dinitrogen monoxide gas source 84, hydrogen chloride gas source 85, andoxygen gas source 86. Valves V3, V4, V5, and V6, and mass flowcontrollers MF3, MF4, MF5, and MF6 are connected to the four branchpipes. The oxygen gas sources 82 and 86 can be one common gas source.

[0070] The operation of the heat-treating apparatus shown in FIG. 1 willbe described. With this apparatus, a wet oxidation process, dryoxidation process, oxinitriding process, and the like can be selectivelyperformed for, e.g., a wafer as a target substrate with a silicon layerexposed on its surface. In the following description, the operations andeffects of the dry oxidation process, a gettering process, theoxinitriding process, the wet oxidation process, and diluted wetoxidation process will be described sequentially.

[0071] (Dry Oxidation Process)

[0072] When the main controller 57 selects the dry oxidation process, itsends operation signals for the dry oxidation process to theheat-treating unit 11, combustor 12, heating unit 13, and gasdistributor 14.

[0073] In the heat-treating unit 11, a large number of, e.g., 25 to 150,semiconductor wafers W as the target substrates are held like shelves bythe wafer boat 3. The interior of the reaction tube 21 is heated by theheater 22 in advance to a predetermined temperature. The semiconductorwafers W are loaded into the reaction tube 21 by the wafer boat elevator30. The opening 25 as the furnace opening is hermetically closed by thelid 34 (the state of FIG. 1). Successively, the temperature in thereaction tube 21 is raised to a predetermined temperature, e.g., 800°C., and is stabilized.

[0074] In the step of loading the wafers W and the step of raising thetemperature in the reaction tube 21, for example, nitrogen gas slightlymixed with oxygen gas is supplied from a gas supply pipe (not shown)into the reaction tube 21. When the interior of the reaction tube 21reaches the process temperature, gas supply is stopped. The interior ofthe reaction tube 21 is evacuated by the exhaust means 15 through theexhaust pipe 20. Thus, the interior of the reaction tube 21 is slightlypressure-reduced. In this state, the temperature of the wafers W isstabilized. Then, the oxidation process is performed.

[0075] The heating unit 13 is turned on. The power supply amount to theheater 63 and the cooling water supply amount to the cooling jacket 66are controlled, so the interior of the heating chamber 61 reaches apreset temperature of, e.g., 1,000° C. In the gas distributor 14, thevalves V6 and V5 are opened. The oxygen gas and hydrogen chloride gas,respectively adjusted to predetermined flow rates by the mass flowcontrollers MF6 and MF5, flow into the heating chamber 61 at flow ratesof, e.g., 10 slm and 1 slm. At this time, the combustor 12 is turnedoff, and the valves VA and VB as the primary side of the combustor 12are closed.

[0076] As shown in FIG. 5A, the process gases flow in the gaps of thebreathing resistance member 62 through a thermally uniformizing tube inthe heating chamber 61 while coming into contact with the breathingresistance member 62. While flowing in the heating chamber 61, theprocess gases are heated to, e.g., near 1,000° C. Hence, the oxygen gasand hydrogen chloride gas react as in the following formulas, so a smallamount of water vapor on the order of, e.g., several hundred ppm, may begenerated.

2HCl→H₂+C1 ₂

H₂+1/2O₂→H₂O

[0077] The process gases heated in this manner are supplied to theheat-treating furnace 2 through the second and first gas supply pipes 42and 41. The process gases shift upward inside the thermally uniformizingtube 23 while being heated, and flow into the upper portion of thereaction tube 21. Furthermore, the process gases are supplied to theprocess region in the reaction tube 21 through the gas holes 21 b, andare exhausted from the lower exhaust pipe 20. During this period oftime, the process gases enter among the wafers W held like shelves, tosubject the wafers W to a predetermined process. More specifically, thechloride gas removes (gettering) contaminant metals on the wafersurface. The oxygen gas oxidizes the silicon layer on the surface of thewafer W, thus forming a silicon oxide film. These process gases containa small amount of water vapor, as described above. The oxide film growsbecause of the water vapor.

[0078] During this process, the process gases from the heating unit 13flow to the combustor 12 through the second and first gas supply pipes42 and 41. If the valves VA and VB connected to the first and second gasinlet pipes 71 and 72, respectively, of the combustor 12 are closed, theprocess gases merely enter the combustion chamber 59, and do not flow tothe upstream side of the combustion chamber 59.

[0079] The silicon oxide film formed by the dry oxidation processaccording to this embodiment has excellent characteristics in both theplanar uniformity and inter-planar uniformity of the thickness. This maybe due to the following reason. The process gases (the gas mixture ofthe oxygen gas and hydrogen chloride gas) are heated by the heating unit13 to, e.g., near 1,000° C., and activated, so they are thermallydecomposed. Thus, small amounts of water vapor and chloride aregenerated. Even the temperature decreases, the water vapor and chlorideonce generated in the process gases do not reduce in amount. Assume thatwater vapor and chloride are generated by the heating unit 13 at atemperature higher than the process temperature in the reaction tube 21.Even if the process gases are cooled while they flow through the secondand first gas supply pipes 42 and 41 on the secondary side, changes inthe process gases are small. Even when the process gases are heated inthe reaction tube 21 after that, they generate no more water vapor.

[0080] In other words, the process gases are activated by the heatingunit 13 and are thermally decomposed sufficiently. When the processgases enter among the wafers W stacked in the wafer boat 3, they havegenerated water vapor and chloride almost completely. Therefore, theamounts of water vapor and chloride contained in the process gasesflowing from the periphery toward the center of each wafer W are almostthe same at any position. As a result, even on the wafer W located atthe upper side of the wafer boat 3, the film formation operation by thewater vapor and the gettering operation by chloride take place to almostthe same degree within the wafer surface. Hence, the planar uniformityof the thickness becomes good.

[0081] Furthermore, in the prior art, the lower on the lower side of thewafer boat 3, the more generation of water vapor and chlorideprogresses. On the upper side, the thickness uniformity is poor. Thelower the position of the wafer, the better the thickness uniformity. Incontrast to this, with the dry oxidation process according thisembodiment, the generation reaction that occurs on the lower side whenno heating unit 13 is used has already occurred on the upper side.Hence, variations in thickness distribution among the wafers W decrease,and the inter-planar uniformity of the thickness becomes good.

[0082] Strictly, the temperature is higher at the center than at theperiphery of the wafer W, so the thickness tends to increase at thecenter in the first place. When, however, the hydrogen chloride gas andoxygen gas are heated by the heating unit 13 to perform dry oxidation,the film at the peripheral region grows, and consequently the thicknessuniformity becomes good. This may be due to the following reason. In thereaction tube 21, the water vapor and chloride obtained in the heatingunit 13 flow from the periphery toward the center of the wafer W. Hence,the concentrations of the process gases may slightly decrease toward thecenter. As a result, film formation and gettering at the peripheryprogress largely, so the operation of increasing the thickness at theperiphery acts.

[0083] Since the process gases are heated by using the heating unit 13,they can be activated sufficiently. In the heating unit 13, the heatingchamber 61 is formed of quartz, and the heater 63 has a specialarrangement. Hence, the heating chamber 61 can be heated to a hightemperature of, e.g., 800° C. or more. As described above, the heater 63has a special structure formed of a string-like body and, e.g., ahelical quartz tube. The string-like body is formed by knitting togethera plurality of bundles of carbon fibers containing a small amount ofmetal impurities. The quartz tube accommodates and seals the string-likebody.

[0084] The breathing resistance member 62 is formed in the heatingchamber 61, and the process gases are heated as they come into contactwith the breathing resistance member 62. Thus, the temperatures of theprocess gases increase efficiently. The breathing resistance member 62is filled in the heating chamber 61. Thus, the process gases flow in theheating chamber 61 while coming into contact with the breathingresistance member 62. This prolongs the stay time of the process gases.The process gases are heated by combination of heating by convection ofthe process gases themselves heated by the heater 63, and heating byheat transfer from the breathing resistance member 62.

[0085] As the breathing resistance member 62, for example, quartz pieces(e.g., beads) each having a diameter of about φ1 to φ10 are used. As thequartz pieces 62 have a large entire surface area, a large heat transferarea can be reserved, so the process gases can be heated efficiently.The heating chamber 61 and second gas supply pipe 42 are connected toeach other. Thus, the process gases sufficiently activated by theheating chamber 61 are supplied to the second gas supply pipe 42 whilemaintaining a high-temperature state. Since the process gases aresupplied to the reaction tube 21 while holding a high active degree, aprocess with a good planar uniformity and inter-planar uniformity of thethickness can be performed, as described above.

[0086] (Gettering Process)

[0087] A gettering process is performed for removing the contaminantmetals on the wafer surface. When the main controller 57 selects thegettering process, it sends operation signal for the gettering processto the heat-treating unit 11, combustor 12, heating unit 13, and gasdistributor 14.

[0088] In the heat-treating unit 11, a large number of wafers W are heldlike shelves by the wafer boat 3. The interior of the reaction tube 21is heated by the heater 22 in advance to a predetermined temperature.The wafers W are loaded into the reaction tube 21 by the wafer boatelevator 30. The opening 25 as the furnace opening is hermeticallyclosed by the lid 34 (the state of FIG. 1). Successively, thetemperature in the reaction tube 21 is raised to a predeterminedtemperature, e.g., 900° C., and is stabilized.

[0089] The heating unit 13 is turned on. The power supply amount to theheater 63 and the cooling water supply amount to the cooling jacket 66are controlled, so the interior of the heating chamber 61 reaches apreset temperature of, e.g., 1,000° C. In the gas distributor 14, thevalves V6 and V5 are opened. Small amounts of oxygen gas and hydrogenchloride gas, respectively adjusted to predetermined flow rates by themass flow controllers MF6 and MF5, flow into the heating chamber 61 atflow rates of, e.g., 0.01 slm to 1 slm and 0.01 slm to 1 slm. At thistime, the combustor 12 is turned off, and the valves VA and VB as theprimary side of the combustor 12 are closed.

[0090] As shown in FIG. 5B, the process gases flow in the gaps of thebreathing resistance member 62 through a thermally uniformizing tube inthe heating chamber 61 while coming into contact with the breathingresistance member 62. While flowing in the heating chamber 61, theprocess gases are heated to, e.g., near 1,000° C. Hence, the hydrogenchloride gas and oxygen gas react, so the hydrogen chloride gas andhydrogen gas are present in the mixed state. The process gases heated inthis manner are supplied to the heat-treating furnace 2 through thesecond and first gas supply pipes 42 and 41. In the reaction tube 21,the process gases enter among the wafers W held like shelves, to subjectthe wafers W to a predetermined process. More specifically, the hydrogenchloride gas and chloride gas remove (gettering) contaminant metals onthe wafer surface. The predetermined gettering process is performed inthis manner. Successively, e.g., a wet oxidation process is performed.

[0091] With the gettering process according to this embodiment, sincethe hydrogen chloride gas and oxygen gas are sufficiently heated andactivated in the heating unit 13, they react sufficiently. Hence,hydrogen chloride, hydrogen, and a small amount of water vapor, whichare reaction products, are present in the mixed state. The getteringeffect is large, so the efficiency with which the metal on the wafersurface is removed is improved. Accordingly, when a wet oxidationprocess is to be performed successively, an oxide film is formed on thewafer surface where metals are removed. As a result, a high-quality filmcan be obtained.

[0092] (Oxinitriding Process)

[0093] When the main controller 57 selects the oxinitriding process, itsends operation signals for the oxinitriding process to theheat-treating unit 11, combustor 12, heating unit 13, and gasdistributor 14.

[0094] In the heat-treating unit 11, a large number of wafers W are heldlike shelves by the wafer boat 3. The interior of the reaction tube 21is heated by the heater 22 in advance to a predetermined temperature.The wafers W are loaded into the reaction tube 21 by the wafer boatelevator 30. The opening 25 as the furnace opening is hermeticallyclosed by the lid 34 (the state of FIG. 1). Successively, thetemperature in the reaction tube 21 is raised to a predeterminedtemperature, e.g., 800° C., and is stabilized.

[0095] The heating unit 13 is turned on. The power supply amount to theheater 63 and the cooling water supply amount to the cooling jacket 66are controlled, so the interior of the heating chamber 61 reaches apreset temperature of, e.g., 900° C. to 1,000° C. In the gas distributor14, the valve V4 is opened. Dinitrogen monoxide gas, adjusted togapredetermined flow rate by the mass flow controller MF4, flows into theheating chamber 61 at a flow rate of, e.g., 1 slm to 10 slm. At thistime, the combustor 12 is turned off, and the valves VA and VB as theprimary side of the combustor 12 are closed.

[0096] As shown in FIG. 5C, the dinitrogen monoxide gas flows in thegaps of the breathing resistance member 62 through a thermallyuniformizing tube in the heating chamber 61 while coming into contactwith the breathing resistance member 62. While flowing in the heatingchamber 61, the dinitrogen monoxide gas is heated to, e.g., near thepreset temperature. Hence, the dinitrogen monoxide gas is pre-heated toa temperature close to the decomposition temperature. The dinitrogenmonoxide gas is thus activated to such a degree that it is decomposed assoon as it flows into the reaction tube 21. In FIG. 5C, N₂O* shows N₂Oin the activated state. The dinitrogen monoxide gas heated in thismanner enters the reaction tube 21 to oxidize and nitride the siliconlayer of the wafer W. Hence, a nitrogen-mixed silicon oxide-film isformed.

[0097] With the oxinitriding process according to this embodiment, theformed nitrogen-containing silicon oxide film has excellentcharacteristics in both the planar uniformity and inter-planaruniformity of the thickness. This may be due to the following reason.The dinitrogen monoxide gas is heated by the heating unit 13 to, e.g.,near 900° C. to 1,000° C., and is activated in advance to a stateimmediately before decomposition. When the dinitrogen monoxide gasenters the reaction tube 21 and reaches the upper side of the wafer boat3, it has already been decomposed to a considerable degree. Even if thetemperature in the reaction tube 21 is low, the dinitrogen monoxide gasis activated sufficiently, so the silicon oxide film can be heavilydoped with nitrogen.

[0098] At this time, when the dinitrogen monoxide gas flows from theperiphery toward the center of the wafer W, the decomposition degreedoes not substantially differ between the periphery and center. Theamount of active species generated by the decomposition of dinitrogenmonoxide is almost the same or does not differ very much at anyposition. Hence, the planar uniformity of the thickness becomes goodeven in a wafer W located at the upper side of the wafer boat 3. Withthe oxinitriding process according to this embodiment, the generationreaction occurring on the lower side when the heating unit 13 is notused has already occurred on the upper side. Hence, variations inthickness distribution among the wafers W decrease, and the inter-planaruniformity of the thickness becomes good.

[0099] In this manner, with the oxinitriding process according to thisembodiment, even if the temperature of the reaction tube 21 is low, thefilm can be heavily doped with nitrogen. Also, the planar uniformity andinter-planar uniformity of the thickness can be improved.

[0100] (Wet Oxidation Process)

[0101] When the main controller 57 selects the wet oxidation process, itsends operation signals for the wet oxidation process to theheat-treating unit 11, combustor 12, heating unit 13, and gasdistributor 14.

[0102] In the heat-treating unit 11, a large number of wafers W are heldlike shelves by the wafer boat 3. The interior of the reaction tube 21is heated. by the heater 22 in advance to a predetermined temperature.The wafers W are loaded into the reaction tube 21 by the wafer boatelevator 30. The opening 25 as the furnace opening is hermeticallyclosed by the lid 34 (the state of FIG. 1). Successively, thetemperature in the reaction tube 21 is raised to a predeterminedtemperature, e.g., 900° C., and is stabilized.

[0103] The combustor 12 is turned on. The power supply amount to theheater 53 is controlled, so the interiors of the heating spaces 52A and52B reach preset temperatures of, e.g., 900° C. to 950° C. In the gasdistributor 14, the valves V1 and V2 are opened. Hydrogen gas and oxygengas, adjusted to predetermined flow rates by the mass flow controllersMF1 and MF2, flow into the combustor 12 at flow rates of, e.g., 3 slm to10 slm and 3 slm to 10 slm. The heating unit 13 is turned off.Accordingly, power supply to the heater 63 and cooling water supply tothe cooling jacket 66 are not performed. In the gas distributor 14,however, the valve V3 is opened, so nitrogen gas, adjusted to apredetermined flow rate by the mass flow controller MF3, flows into theheating chamber 61 at a flow rate of, e.g., 50 sccm to 500 sccm. Inplace of the nitrogen gas, oxygen gas may flow into the heating chamber61.

[0104] As shown in FIG. 6A, the hydrogen gas and oxygen gas are heatedby the inner and outer heating spaces 52A and 52B, respectively, of thecombustor 12. Part of the oxygen gas and the hydrogen gas causecombustion reaction in the combustion chamber 59 to generate watervapor. Oxygen gas and water vapor generated in this manner are suppliedto the heat-treating furnace 2 through the first gas supply pipe 41. Asmall amount of nitrogen gas that has passed through the heating unit 13is also supplied to the heat-treating furnace 2 through the second andfirst gas supply pipes 42 and 41. In the reaction tube 21, a process gasas the mixture of these gases enters among the wafers W held likeshelves, to subject the wafers W to a predetermined process. Morespecifically, the oxygen gas and water vapor oxidize the silicon layeron the wafer surface, thus forming a silicon oxide film.

[0105] With the wet oxidation process according to this embodiment, thecombustion reaction of part of the oxygen gas and the hydrogen gasoccurs sufficiently in the combustor 12, so they are supplied to thereaction tube 21 after it has already generated water vapor. almostcompletely. Hence, the amounts of water vapor and oxygen contained inthe process gas flowing from the periphery toward the center of thewafer W are almost the same at any position. As the supply degrees ofthe water vapor and oxygen in the surface of the wafer W are almost thesame, even when the process temperature is decreased, the planaruniformity of the thickness becomes good.

[0106] At this time, since the nitrogen gas is supplied to the heatingunit 13, the flow of the gas from the combustor 12 to the heating unit13 can be prevented. More specifically, the second gas supply pipe 42 isformed of quartz. When the heating unit 13 heats the process gas, thesecond gas supply pipe 42 reaches a considerably high temperature.Hence, no valves for supplying gases and stopping gas supply can beconnected to the second gas supply pipe 42. If the, gases are notsupplied from the heating unit 13, the water vapor generated in thecombustor 12 undesirably enters-the heating chamber 61 through thesecond gas supply pipe 42. Once the water vapor is adsorbed by thebreathing resistance member 62 filled in the heating chamber 61, itcannot be removed easily. Assume that in this state, the dry oxidationprocess is to be performed in the following step. Then, the water vaporamount supplied to the reaction tube 21 changes, and the processrepeatability degrades. Consequently, the planar uniformity of thethickness decreases. In view of this, to prevent flowing of the gas fromthe combustor 12 to the heating unit 13 is effective.

[0107] (Diluted Wet Oxidation Process)

[0108] A diluted wet oxidation process is the following process. Aprocess gas containing oxygen and water vapor used in the wet oxidationprocess described above is diluted with a small amount of nitrogen gas.Then, the diluted process gas is supplied into the reaction tube 21.When the main controller 57 selects the diluted wet oxidation process,it sends operation signals for the diluted wet oxidation process to theheat-treating unit 11, combustor 12, heating unit 13, and gasdistributor 14.

[0109] In the heat-treating unit 11, a large number of wafers W are heldlike shelves by the wafer boat 3. The interior of the reaction tube 21is heated by the heater 22 in advance to a predetermined temperature.The wafers W are loaded into the reaction tube 21 by the wafer boatelevator 30. The opening 25 as the furnace opening is hermeticallyclosed by the lid 34 (the state of FIG. 1). Successively, thetemperature in the reaction tube 21 is raised to a predeterminedtemperature, e.g., 850° C., and is stabilized.

[0110] The combustor 12 is turned on. The power supply amount to theheater 53 is controlled, so the interiors of the heating spaces 52A and52B reach preset temperatures of, e.g., 900° C. to 950° C. In the gasdistributor 14, the valves V1 and V2 are opened. Hydrogen gas and oxygengas, adjusted to predetermined flow rates by the mass flow controllersMF1 and MF2, flow into the combustor 12 at flow rates of, e.g., 3 slmand 3 slm, respectively. The heating unit 13 is also turned on. Thepower supply amount to the heater 63 and the cooling water supply amountto the cooling jacket 66 are controlled so the interior of the heatingchamber 61 reaches a preset temperature of, e.g., 1,000° C. In the gasdistributor 14, the valve V3 is opened, so nitrogen gas, adjusted to apredetermined flow rate by the mass flow controller MF3, flows into theheating chamber 61 at a flow rate of, e.g., 15 slm.

[0111] As shown in FIG. 6B, the nitrogen gas flows in the gaps of thebreathing resistance member 62 through a thermally uniformizing tube inthe heating chamber 61 while coming into contact with the breathingresistance member 62. As the nitrogen gas flows in the heating chamber61, it is heated to, e.g., near 1,000° C. The nitrogen gas pre-heated inthis manner is supplied to the first gas supply pipe 41 through thesecond gas supply pipe 42. The nitrogen gas is then mixed with theprocess gas containing the oxygen gas and water vapor which flows fromthe combustor 12. Hence, the process gas is supplied to theheat-treating furnace 2 as it is diluted by the nitrogen gas. In thereaction tube 21, the process gas as a gas mixture of these gases entersamong the wafers W held like shelves, and subjects the wafers W to apredetermined manner. More specifically, the oxygen gas and water vaporoxidize the silicon layer on the wafer surface to form a silicon oxidefilm.

[0112] With the diluted wet oxidation process according to thisembodiment, the nitrogen gas is mixed with the process gas containingthe oxygen gas and water vapor after it is sufficiently pre-heated bythe heating unit 13. Therefore, the temperature of the process gas 10does not decrease due to mixture with the nitrogen gas. Consequently, aprocess with a good planar uniformity of the thickness can be performed.

[0113] In other words, when the nitrogen gas which is not heated ismixed with the process gas as in the conventional manner, thetemperature of the process gas decreases. When the process gas with adecreased temperature is supplied to the reaction tube 21 to perform aprocess, the film thickness tends to decrease near the periphery of thewafer W. In contrast to this, in the diluted wet oxidation processaccording to this embodiment, the nitrogen gas is sufficientlypre-heated by the heating unit 13 in advance. Then, a temperaturedecrease of the process gas can be suppressed, so a decrease in planaruniformity in thickness can be prevented.

[0114] As described above, in the heat-treating apparatus shown in FIG.1, the combustor 12 and heating unit 13 are disposed in a parallelmanner. Therefore, the wet oxidation process utilizing the combustor 12;the dry oxidation process, oxinitriding process, and gettering processutilizing the heating unit 13; and the diluted wet oxidation processutilizing both the combustor 12 and heating unit 13 can be performedselectively. In addition, a good result can be obtained with eachprocess.

[0115] When a wet oxidation process apparatus having only the combustor12 is used, if the combustor 12 heats oxygen gas and hydrogen chloridegas, the wet oxidation process and dry oxidation process can beperformed. However, the heated oxygen gas is cooled while it passesthrough the combustion chamber 59 at the next stage of the combustor 12.Thus, the oxygen gas when being supplied to the heat-treating furnace 2has a low active degree. Therefore, it is difficult to perform a processwith a good planar uniformity of the thickness.

[0116] In contrast to this, with the heat-treating apparatus shown inFIG. 1, the oxygen gas heated by the heating unit 13 can be supplied tothe heat-treating furnace 2 while maintaining its active degree.Therefore, a high planar uniformity of the thickness can be ensured asdescribed above.

[0117] With the heat-treating apparatus shown in FIG. 1, various typesof processes can be performed well with one heat-treating apparatus.Thus, the range of choice of the processes becomes wide. This isadvantageous in terms of cost and space efficiency. Since the processesdescribed above can be performed with one heat-treating apparatus, aplurality of processes can be continuously performed in the followingaspects with the wafers being accommodated in the reaction tube 21.

[0118] Assume that the gettering process and wet oxidation process areto be combined. The gettering process is performed first with the wafersW being accommodated in the reaction tube 21. Successively, the wetoxidation process is performed continuously. In this case, the metal onthe water surface is removed by the gettering process. In this state, awet oxide film is formed. Therefore, a film with a high quality can beformed.

[0119] Assume that a gate oxide film is to be formed by combining thewet oxidation process and dry oxidation process. These two processes canbe performed alternately and continuously. In this case, the wetoxidation process is performed first with the wafers W beingaccommodated in the reaction tube 21. Then, the interior of the reactiontube 21 is purged with, e.g., nitrogen gas. The dry oxidation process isperformed next. The interior of the reaction tube 21 is then purgedwith, e.g., nitrogen gas. Then, the wet oxidation process is performedagain. In this manner, the wet oxidation process and dry oxidationprocess can be performed alternately. When the wet oxidation process anddry oxidation process are to be combined, they may be performedsimultaneously in the same time zone.

[0120] Similarly, the wet oxidation process and oxinitriding process, orthe wet oxidation process, dry oxidation process, and oxinitridingprocess can be performed continuously. In the latter case, the wetoxidation process is performed first with the wafers W beingaccommodated in the reaction tube 21. Then, the interior of the reactiontube 21 is purged with, e.g., nitrogen gas. The dry oxidation process isperformed. The interior of the reaction tube 21 is then purged with,e.g., nitrogen gas. Finally, the oxinitriding process is performed.

[0121] As the gas to be used in the dry oxidation process or getteringprocess, in place of the hydrogen chloride gas, other compound gasescontaining hydrogen and chloride, e.g., dichloroethylene gas (C₂H₂Cl₂),can be used. As the breathing resistance member 62 to be provided to theheating unit 13, in place of that of this embodiment, one having thefollowing structure can be used. Namely, a plurality of breathing plateswith a large number of breathing holes are arrayed in the breathingdirection so as to stand in the way of the flow channel.

[0122] The second gas supply pipe 42 can form a double pipe at thedownstream portion of the heating chamber 61. In this case, an outerpipe is present between the atmosphere and the inner pipe through whichthe gas flows. The inner pipe does not come into contact with theatmosphere. Hence, the amount of heat dissipated by the heated processgas as the process gas flows through the inner pipe decreases. Theprocess gas can be introduced to the first gas supply pipe 41 while itis kept activated by heating.

[0123] An orifice (a portion where the pipe diameter decreases sharply)may be formed on the second gas supply pipe 42 between the heating unit13 and reaction tube 21. The orifice causes a pressure loss. Even if apressure-reducing process is performed in the process chamber, thedegree of pressure reduction in the heating chamber 61 becomes small. Inthis case, in the pressure-reducing process as well, the degree withwhich convection in the heating chamber 61 is interfered with is small.Also, the partial pressure of the process gas in the heating chamber 61increases. Therefore, heat conduction due to convection of the processgas in the heating chamber 61 tends to occur more easily than in a casewherein no orifice is formed. Thus, the process gas can be sufficientlyheated to a predetermined temperature.

Experiment

[0124] (Dry Oxidation Process)

[0125] Experiments were performed under the process conditions describedin (Dry Oxidation Process) of the embodiment described above. Anexperiment according to the embodiment of the present invention wasperformed as follows. A dry oxidation process was performed whileheating the process gas with the heating unit 13 (by turning on theheater 63 of the heating unit 13). The process time was 90 minutes. Asilicon oxide film with a thickness of 10 nm was formed. As acomparative example, a dry oxidation process was performed under thesame process conditions except that the process gas was not heated (byturning off the heater 63 of the heating unit 13).

[0126]FIGS. 7A and 7B are graphs showing the interplanar uniformity andplanar uniformity, respectively, as experimental results obtained whenthe dry oxidation process is performed by using the heat-treatingapparatus shown in FIG. 1. In FIG. 7A,the axis of abscissa representsthe average inter-planar uniformity of the thickness, and the axis ofordinate represents whether heating is performed. In FIG. 7B, the axisof abscissa represents the average planar uniformity of the thickness,and the axis of ordinate represents the positions of the wafers W on thewafer boat 3. In FIGS. 7A and 7B, the hatched columns show cases withthe process gas being heated, and the non-hatched columns show caseswith the process gas being not heated.

[0127] The smaller the inter-planar uniformity and planar uniformity ofthe thickness, the higher the uniformities. As shown in FIG. 7A, whenthe process gas was heated, the average inter-planar uniformity wassmaller than in a case wherein the process gas was not heated. Namely,it was confirmed that when the process gas was heated by the heatingunit 13, the inter-planar uniformity was improved. As shown in FIG. 7B,when the process gas was heated, at any position on the upper side,middle side, or lower side of the wafer boat 3, the average planaruniformity was smaller than in the case wherein the process gas was notheated. Namely, it was confirmed that when the process gas was heated bythe heating unit 13, the planar uniformity was improved.

[0128] (Oxinitriding Process)

[0129] Experiments were performed under the process conditions describedin (Oxinitriding Process) of the embodiment described above. Anexperiment according to the embodiment of the present invention wasperformed as follows. An oxinitriding process was performed whileheating the process gas with the heating unit 13 (by turning on theheater 63 of the heating unit 13). The process temperature in thereaction tube 21 was set to 800° C. The process pressure in the reactiontube 21 was set to 93.1 kPa. The temperature of the heating unit 13 wasset to 1,000° C. The flow rate of the dinitrogen monoxide gas was set to5 slm. The process time was 7.5 min. A nitrogen-containing silicon oxidefilm with a thickness of 2.5 nm was formed. As a comparative example, anoxinitriding process was performed under the same process conditionsexcept that the process gas was not heated (by turning off the heater 63of the heating unit 13).

[0130]FIGS. 8A and 8B are graphs showing the experimental resultsobtained when the oxinitriding process is performed by using theheat-treating apparatus shown in FIG. 1 and by turning on/off theheater. In FIGS. 8A and 8B, the axis of abscissa represents depth in thefilm, and the axis of ordinate represents the nitrogen concentration inthe film.

[0131] As shown in FIGS. 8A and 8B, when the dinitrogen monoxide gas washeated, the nitrogen concentration in the film was greatly larger thanin a case wherein the process gas was not heated. Namely, it wasconfirmed that when the dinitrogen monoxide gas was heated by theheating unit 13, a silicon oxide film containing a high concentration ofnitrogen was formed.

[0132] (Diluted Wet Oxidation Process)

[0133] Experiments were performed under the process conditions describedin (Diluted Wet Oxidation Process) of the embodiment described above. Anexperiment according to the embodiment of the present invention wasperformed as follows. A diluted wet oxidation process was performedwhile heating the nitrogen gas with the heating unit 13 (by turning onthe heater 63 of the heating unit 13). The process was performed withoutrotating the wafer boat 3. A silicon oxide film with a thickness of 6 nmwas formed. As a comparative example, a diluted wet oxidation processwas performed under the same process conditions except that the nitrogengas was not heated (by turning off the heater 63 of the heating unit13).

[0134]FIG. 9 is a graph showing an experimental result obtained when adiluted wet oxidation process was performed by using the heat-treatingapparatus shown in FIG. 1. In FIG. 9, the axis of abscissa representsthe positions of the wafers W on the wafer boat 3, and the axis ofordinate represents the planar uniformity. In FIG. 9, (o) indicatescases with the nitrogen gas being heated, and (x) indicates cases withthe nitrogen gas being not heated.

[0135] As shown in FIG. 9, when the nitrogen gas was heated, at anyposition on the upper side, middle side, or lower side of the wafer boat3, the average planar uniformity was smaller than in the case whereinthe process gas was not heated. Namely, it was confirmed that when thenitrogen gas was heated by the heating unit 13, the planar uniformity ofthe thickness was improved.

[0136] The present invention is not limited to the above embodiments.When practicing the present invention, it can be modified in variousmanners without departing from its spirit and scope. The embodiments maybe practiced in appropriate combinations as much as possible. In thiscase, a combined effect can be obtained.

1. (Amended) A heat-treating apparatus for a semiconductor process,comprising: a process chamber which accommodates a target substrate; asupport member which is disposed in the process chamber and supports thetarget substrate; a heater which heats the target substrate accommodatedin the process chamber; an exhaust system to evacuate an interior of theprocess chamber; and a supply system to supply a process gas into theprocess chamber, wherein the supply system comprises a combustor whichis disposed outside the process chamber and has a combustion chamber,the combustor serving to generate water vapor by reaction of hydrogengas and oxygen gas in the combustion chamber and supply the water vaporto the process chamber, a heating unit which is disposed outside theprocess chamber and has a heating chamber, the heating unit serving toselectively heat a gas not passing through the combustion chamber to atemperature not lower than an activating temperature of the gas andsupply the gas to the process chamber, and a gas distributor whichselectively supplies hydrogen gas and oxygen gas to the combustionchamber and selectively supplies a reactive gas and inactive gas to theheating chamber, wherein the heating chamber is made of quartz, and aheating member is disposed to surround the heating chamber, the heatingmember comprising a heating resistor containing a small mount of metalimpurities and an insulating sealing body for sealing the heatingresistor.
 2. The apparatus according to claim 1, further comprising acontroller which controls the combustor, the heating unit, and the gasdistributor so as to use the combustor and the heating unit selectively.3. The apparatus according to claim 1, wherein the gas distributorsupplies an inactive gas to the process chamber through the combustionchamber, so as to prevent the water vapor from entering the heatingchamber when the water vapor is supplied from the combustor to theprocess chamber.
 4. The apparatus according to claim 1, wherein theheating unit heats gas in the heating chamber to 300° C. to 1,100° C. 5.The apparatus according to claim 1, wherein the heating unit has abreathing resistance member which is disposed in and heated by theheating chamber.
 6. The apparatus according to claim 5, wherein thebreathing resistance member comprises a large number of piecessubstantially made of a material selected from the group consisting ofquartz and ceramic materials.
 7. The apparatus according to claim 1,wherein the gas distributor supplies as the reactive gas, oxidizing gas,oxinitriding gas, and a compound gas containing hydrogen and chlorideselectively.
 8. The apparatus according to claim 1, wherein the gasdistributor supplies nitrogen gas as the inactive gas.
 9. The apparatusaccording to claim 1, wherein the supply system comprises a common inletpipe connected to the process chamber, the combustion chamber andheating chamber being connected to the common inlet pipe.
 10. (Deleted)11. (Amended) The apparatus according to claim 1, wherein the heatingresistor is made of a string-like body formed by knitting a high-puritycarbon material.
 12. (Amended) The apparatus according to claim 1,wherein the sealing body is substantially made of a material selectedfrom the group consisting of quartz and ceramic materials.
 13. Theapparatus according to claim 1, wherein the support member supports inthe process chamber a plurality of target substrates at gaps in avertical direction.
 14. (Deleted)
 15. (Deleted)
 16. (Amended) Aheat-treating method for a semiconductor process, comprising the stepsof: accommodating a target substrate in a process chamber; heating thetarget substrate accommodated in the process chamber, performing a wetoxidation process of oxidizing the target substrate to form an oxidefilm by supplying water vapor to the process chamber while makinghydrogen gas react with oxygen gas to generate the water vapor by acombustor which is disposed outside the process chamber and has acombustion chamber, and subjecting the target substrate to a firstprocess other than a wet oxidation process by supplying a reactive gasto the process chamber while heating the reactive gas to a temperaturenot less than an activating temperature of the reactive gas by a heatingunit which is disposed outside the process chamber and has a heatingchamber, wherein in the wet oxidation process, an inactive gas issupplied to the process chamber through the heating chamber, so as toprevent water vapor from entering the heating chamber when the watervapor is to be supplied from the combustor to the process chamber. 17.The method according to claim 16, wherein the reactive gas contains anoxidizing gas and a compound gas containing hydrogen and chloride, andthe first process is a dry oxidation process of forming an oxide film byoxidizing the target substrate.
 18. The method according to claim 16,wherein the reactive gas contains an oxidizing gas and a compound gascontaining hydrogen and chloride, and the first process is a getteringprocess of removing a metal from a surface of the target substrate. 19.The method according to claim 16, wherein the reactive gas containsoxinitriding gas, and the first process is an oxinitriding process offorming a nitrogen-containing oxide film by oxinitriding the targetsubstrate.
 20. The method according to claim 16, wherein the wetoxidation process and the first process are performed alternately. 21.The method according to claim 16, wherein the wet oxidation process andthe first process are performed substantially simultaneously. 22.(Deleted)
 23. (Added) The apparatus according to claim 1, wherein acooling member is disposed in addition to the heating member around theheating unit, so that temperature of the heating chamber is controlledby means of interaction between the heating chamber and the coolingmember.
 24. (Added) The apparatus according to claim 1, wherein anorifice is disposed in a pipe through which gas heated by the heatingunit is supplied to the process chamber.
 25. (Added) The apparatusaccording to claim 1, wherein a pipe through which gas heated by theheating unit is supplied to the process chamber is formed of adouble-pipe, and gas heated by the heating unit flows through an innerpipe of the double-pipe.
 26. (Added) The method according to claim 16,further comprising a step of performing a diluted wet oxidation processof oxidizing the target substrate to form an oxide film by supplyingwater vapor to the process chamber while making hydrogen gas react withoxygen gas to generate the water vapor by the combustor, and supplyingnitrogen gas to the process chamber while heating the nitrogen gas bythe heating unit.